• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

Troubleshooting electrical wiring after a smoked PMD

WarWagon said:
I believe it's easier than his old guide today. You now have stand alone trans controllers and a 1993 cruise control unit that can make this conversion easy button. If the IP is toast the DB2 cost is near the same.

Back to your actual problem... You smoked the PMD. What exactly is wrong with the wiring harness? IMO it's fine with the short being in the IP like the last one that went out like this. However you are looking at it and can clear this up better. Just trying for you to not throw unneeded parts at it.

Make sure you get a NEW IP not a worn out rebuild from a shady company. It simply gets "old" to swap worn IP's out over and over. Done that myself enough to serve as a bad example.
Click to expand...

@WarWagon, I'll see if I can find anything newer that references the use of the cruise control unit.

Re: the wiring harness: I don't know if something is wrong. Continuity checks out. Visual check didn't show any issues. The PMD smoked from over-current, surely. It was not a "normal" PMD failure. Where that over-current originated is not clear. I'm leaning towards the IP, as you suggest, but my thought was to replace the harness as insurance. Thanks for the tip on new vs. rebuilt.
 
I believe @Twisted Steel Performance can get new IP's. Otherwise you should say what vendor you are going to use as we know what ones are bad ones out there.

I wouldn't bother with a new wiring harness: it doesn't appear to be needed. New parts may not always be good parts...
 
I hate to throw in new parts because a new part has potential to be bad while the old one was ok, farther complicating diagnostics.
But in this case- replace the harness is not a horrible idea - but don’t discard your old one. Identifying the problem is important for reliability or 6 months down the road you might be in the same spot.

Bad grounding or low voltage would also be a cause. Bad power supply anywhere along the route from battery to pmd and ip. It could be the pmd ground itself, engine to battery ground, bad alternator ground or a combination of moderate grounds of them.

The numbers below are for explanation only- I have no clue the real specs. This is just to convey the concept.
Electrical resistance is cumulative, meaning the ohms add up. Lets say 10 ohms is the point of failure for something. If the spacer on the positive battery cable has 2 ohms from corrosion. And negative battery cable has 2 ohms. Now the pmd connection to power on the pin has 2 ohms and the ground wire for the pmd is 2 ohms. You are at 8 ohms so it isn’t failing yet but you don’t know it is close to the limit. Now the ip gets normal wear from use and the specified resistance is supposed to be 1 ohm but yours is at 1.9 ohms. It takes one little hiccup to go from working to not working. A super hot summer day and thr added heat raises the resistance level (which does occur) or you forgot to add lube to the fuel This tank which makes the solenoid/plunger work harder. Maybe your lift pump wears past limits and now the assist isn’t enough and makes it work harder. This will draw more amperage and since the voltage is constant that means the ohms will swing.

This is why having an annual maintenance schedule to remove and clean contacts in corrosion prone areas, and once every couple years for the rest of us becomes an important task with these early electronic controlled vehicles. Modern cars of high caliber over build for these issues but the Hyaundai’s and similar of the world still suffer the same issues. Once corrosion sets in even the very best made cars suffer from it.

Testing out the electrical power supply should be done. A simple spike in voltage from alternator going bad or loose connection could have caused it.
 
Will L. said:
I hate to throw in new parts because a new part has potential to be bad while the old one was ok, farther complicating diagnostics.
But in this case- replace the harness is not a horrible idea - but don’t discard your old one. Identifying the problem is important for reliability or 6 months down the road you might be in the same spot.

Bad grounding or low voltage would also be a cause. Bad power supply anywhere along the route from battery to pmd and ip. It could be the pmd ground itself, engine to battery ground, bad alternator ground or a combination of moderate grounds of them.

The numbers below are for explanation only- I have no clue the real specs. This is just to convey the concept.
Electrical resistance is cumulative, meaning the ohms add up. Lets say 10 ohms is the point of failure for something. If the spacer on the positive battery cable has 2 ohms from corrosion. And negative battery cable has 2 ohms. Now the pmd connection to power on the pin has 2 ohms and the ground wire for the pmd is 2 ohms. You are at 8 ohms so it isn’t failing yet but you don’t know it is close to the limit. Now the ip gets normal wear from use and the specified resistance is supposed to be 1 ohm but yours is at 1.9 ohms. It takes one little hiccup to go from working to not working. A super hot summer day and thr added heat raises the resistance level (which does occur) or you forgot to add lube to the fuel This tank which makes the solenoid/plunger work harder. Maybe your lift pump wears past limits and now the assist isn’t enough and makes it work harder. This will draw more amperage and since the voltage is constant that means the ohms will swing.

This is why having an annual maintenance schedule to remove and clean contacts in corrosion prone areas, and once every couple years for the rest of us becomes an important task with these early electronic controlled vehicles. Modern cars of high caliber over build for these issues but the Hyaundai’s and similar of the world still suffer the same issues. Once corrosion sets in even the very best made cars suffer from it.

Testing out the electrical power supply should be done. A simple spike in voltage from alternator going bad or loose connection could have caused it.
Click to expand...

Great advice @Will L. . Thanks.
 
WarWagon said:
I believe @Twisted Steel Performance can get new IP's. Otherwise you should say what vendor you are going to use as we know what ones are bad ones out there.

I wouldn't bother with a new wiring harness: it doesn't appear to be needed. New parts may not always be good parts...
Click to expand...
I don't think new is going to work in my budget for this repair. I'm seeing nothing below $1700. Looking at remans from Quadstar (don't know who he uses to rebuild) or AC Delco or Dipaco. There are others that seem legit, too. If you've got suggestions, I'm all ears. There's also a Stanadyne repair shop near Atlanta that I will check with.

Any of you know where to find a reman of the updated 5521 DS4? It's got an S suffix. But none of the rebuild sites that I could find have that part number (12561307S or DS4831-5521S). I've seen it new at Leroy, but again, out of the budget.
 
Tinker said:
I don't think new is going to work in my budget for this repair. I'm seeing nothing below $1700. Looking at remans from Quadstar (don't know who he uses to rebuild) or AC Delco or Dipaco. There are others that seem legit, too. If you've got suggestions, I'm all ears. There's also a Stanadyne repair shop near Atlanta that I will check with.

Any of you know where to find a reman of the updated 5521 DS4? It's got an S suffix. But none of the rebuild sites that I could find have that part number (12561307S or DS4831-5521S). I've seen it new at Leroy, but again, out of the budget.
Click to expand...
I found one vendor, SS Diesel, which explicitly states their supplier remans to the 5521S standards. I can't with any of the others, even AC Delco and the larger parts mfgs don't clarify.
 
I have seen many worn out head and rotor IP's. I have lost an engine over a bad governor in an IP. They are a real time eater to change and NON-STOP problems including smoked starters when they have trouble.

The DS4's can have a worn head and rotor and a real PIA to troubleshoot then you get to do the job over.

How much are you saving on a rebuilt/repaired/used IP and is it worth the trouble? $500 isn't much when you add a $200 starter and a $120 tow bill. Just saying.
 
Yes and yes
Yes stay away from ss diesel. Total rip off place. Won’t warranty stuff, their insta heat glowplugs have ruined more diesels than teenagers showing off.

Yes spend the extra money and get a brand new pump. The amount of junk head and rotors out there is ridiculous and only going to get worse with stanandyne not making new one anymore.

get a fuel pressure gauge on there from day one, low pressure ruins the pump quick. So does lack of lube which usedto be diesel fuel but now has to be added. Stanandyne or the 2 stroke. The last bad thing for head and rotor is water. If you get enough water in there to set off the sensor then immediately replace the filter. An upgraded water separator is a good idea if it happens in your area.
If you take care of those things it will help your pump life a ton.
 
You must log in or register to reply here.
Back
Top